Category: Toyota
Posted by Neil Winton on Tue, Nov 3, 2009 at 12:23 PMNew Toyota Prius uses bigger engine to improve fuel economy
The latest Prius is much more fuel-efficient than previous models, although official figures still exaggerate its real-world economy.
Everything about the latest gasoline-electric Toyota Prius III hybrid sold in America and here in Europe is the same, and yet the government figures estimating its average fuel consumption are markedly different.
The U.S. government, in the guise of the EPA, estimates the Prius will average about 50 miles per U.S. gallon, while in Europe the authorities reckon it will get you an extra 10 miles plus, or 60.3 mpg. Both versions are exactly the same, now powered by a 1.8 litre 4-cylinder 134 hp Atkinson gasoline engine and a 60 Kw electric motor.
Toyota claimed in Europe that the previous Prius II, which had a smaller, 1.5 litre gasoline engine, would achieve about 54 mpg. In the real world this was more like 35 mpg. The new one is much more economic - I managed an average 46.4 mpg - but official European Union figures allow Toyota to claim a much higher number - 60.3 mpg.
Toyota has recognized criticism of the old model. Its smaller engine performed well in city driving, but on the highway its lack of power meant it was often operating under strain which hampered fuel efficiency. The Atkinson cycle modifies a traditional engine's compression and exhaust gas cycles to produce power more efficiently.
It is no wonder that there is a big discrepancy between official and actual fuel economy. The European Union's test takes place over a totally flat route consisting of two short drives - 2.5 miles of maximum 31 mph, and 4.3 miles of maximum 75 mph - some accelerating, some cruising, some idling, no air con, wipers, lights, audio or Sat Nav. This produces perfectly comparable data with other cars, but is of absolutely no use at all to those in the real world.
The American test must be a bit more realistic, but it's a shame neither gets close to providing really useful information for buyers.
